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FROST SENSITIVITY OF STONE AND CONCRETE

THE RESULTS OF RESEARCHES CONDUCTED AT C.E.B.T.P. DURING RECENT YEARS ARE SUMMARIZED. FOR STONE SAMPLES THE INHIBITION TEST UNDER VACUUM IS TOO DRASTIC AND IS NON- SELECTIVE. FREEZE-THAW CYCLES YIELD USEFUL RESULTS PROVIDED THE SPECIMEN IS IMMERSED WHILE STILL FROZEN, WHEN THE DEGREE OF SATURATION REACHES A CRITICAL VALUE THE STONE EXPANDS AT SUB-ZERO TEMPERATURE AND THERE IS RISK OF FAILURE. THE LESS THE DIFFERENCES BETWEEN THE EQUILIBRIUM AND CRITICAL (THRESHOLD FOR FROST DAMAGE) CONTENTS OF WATER, THE MORE THE STONE IS LIABLE TO FROST DAMAGE. TOTAL POROSITY IS A DETERMINANT, BUT IS NOT SPECIFIC BY ANY MEANS. PORE-SIZE AND DISTRIBUTION PROVIDE THE MOST VALUABLE DATA FOR WATER ABSORPTION OF STONE, WHILST POROSITY AND LIMITING WATER ABSORPTION CONTENT PERMIT STONES TO BE CLASSIFIED (IN RESPECT OF THEIR FROST RESISTANCE) ACCORDING TO STRUCTURAL POSITION AND EXTERNAL CLIMATE. CONCLUSIONS ON THE MECHANISM OF FREEZING OF FRESH CONCRETE, ON THE MINIMUM STRENGTHS TO PREVENT FAILURE OF THE CONCRETE BY MODERATE FROST, ON THE EFFECT OF FROST ON DIFFERENT QUALITIES OF CONCRETE, AND ON THE PROTECTION OF CONCRETE BY HEAT AT EARLY AGES ARE SUMMARIZED. /AUTHOR/